Alternative strategies to treat potato early blight

Potato, Solanum tuberosum, is a staple crop grown worldwide. Like all other plants that are cultivated in the world’s vast agricultural system, potatoes are constantly under attack by plant pathogens. Early blight is a potato disease caused by a fungal pathogen called Alternaria solani. In Sweden this pathogen is particularly problematic in the starch potato industry causing premature defoliation and reduced starch yield. The most common current treatment is application of fungicides. The focus of the research presented in this thesis has been to test and evaluate alternative ways to combat this pathogen in an applied Swedish field environment. A three-year observational study was conducted, as were multiple field trials, to achieve a broader understanding of how to manage early blight. The results of the observational study led us to design further field trials to test the importance of potassium. We found interesting differences in disease severity among the farms. The field trials consisted of evaluating cultivar tolerance, biological control measures such as the use of biocontrol agents (BCAs) and plant resistance inducers (PRIs), and the role of plant nutrients. The most important finding in this thesis is that the best treatment strategy is highly farm specific, and it is crucial to customize the treatments at a field level. The soil composition is the single largest factor that impacts the rate of infection. A sandier soil is much more likely to suffer from early blight induced yield loss and the recommended treatments should be based on the sand content of the soil in the specific field. Further results conclude that the potassium content in the soil and leaf plays a role in disease rate since a depletion caused heavier infection. The BCAs and PRIs evaluated showed potential for future alternative strategies but none of the evaluated substances proved to be efficient under field conditions. Lastly, it was observed that there are differences among starch potato cultivars currently grown, that affect the disease rate of early blight

Gene Expression and Metabolite Profiling of Thirteen Nigerian Cassava Landraces to Elucidate Starch and Carotenoid Composition

The prevalence of vitamin A deficiency in sub-Saharan Africa necessitates effective approaches to improve provitamin A content of major staple crops. Cassava holds much promise for food security in sub-Saharan Africa, but a negative correlation between beta-carotene, a provitamin A carotenoid, and dry matter content has been reported, which poses a challenge to cassava biofortification by conventional breeding. To identify suitable material for genetic transformation in tissue culture with the overall aim to increase beta-carotene and maintain starch content as well as better understand carotenoid composition, root and leaf tissues from thirteen field-grown cassava landraces were analyzed for agronomic traits, carotenoid, chlorophyll, and starch content. The expression of five genes related to carotenoid biosynthesis were determined in selected landraces. Analysis revealed a weak negative correlation between starch and beta-carotene content, whereas there was a strong positive correlation between root yield and many carotenoids including beta-carotene. Carotenoid synthesis genes were expressed in both white and yellow cassava roots, but phytoene synthase 2 (PSY2), lycopene-epsilon-cyclase (LCY epsilon), and beta-carotenoid hydroxylase (CHY beta) expression were generally higher in yellow roots. This study identified lines with reasonably high content of starch and beta-carotene that could be candidates for biofortification by further breeding or plant biotechnological means

Reduced efficacy of biocontrol agents and plant resistance inducers against potato early blight from greenhouse to field

Early blight in potato, caused by Alternaria solani, is mainly controlled by frequent applications of synthetic fungicides. Reducing the use of synthetic fungicides in agriculture is desired to reach an overall sustainable development since the active components can be harmful for humans and for the ecosystem. In integrated pest management, IPM, the idea is to combine various measures, including optimized crop management, crop rotation, use of resistant cultivars, biological control agents (BCAs), plant resistance inducers, and fertilizers, to decrease the dependence on traditional chemical fungicides. In this paper, we present the results from greenhouse and field trials where we evaluated the effect of strategies aimed at reducing our reliance on synthetic fungicides including treatments with biological control agents (BCAs) (Pythium oligandrum, Polygandron (R), and Bacillus subtilis, Serenade (R)) and plant resistance inducers (silicon products HortiStar (R) and Actisil (R)) for early blight in potato. The agents were applied separately or in combination with each other or with synthetic fungicides. In the greenhouse, trials application of these agents resulted in 50-95% reduction of infection by A. solani, but their combination did not generally improve the outcome. However, the effects were much smaller in the hand-sprayed field trials, 20-25% disease reduction and almost disappeared in full-scale field trials where application was done with tractor sprayers. In this article, we discuss possible reasons behind the drop in efficacy from greenhouse trials to full-size field evaluation

Evidence for Sexual Dimorphism in the Response to TLR3 Activation in the Developing Neonatal Mouse Brain: A Pilot Study

Toll-like receptor (TLR)3 activation during the neonatal period produces responses linked to the origins of neuropsychiatric disorders. Although there is sexual dimorphism in neuropsychiatric disorders, it is unknown if brain responses to TLR3 activation are sex-specific. We hypothesized that poly I:C in a post-natal day (P)8 model induces a sexually dimorphic inflammatory responses. C57BL6 mice received intraperitoneal injection of poly I:C (10 mg/kg) or vehicle [normal saline (NS)] at P8. Pups were killed at 6 or 14 h for caspase 3 and 8 activity assays, NFkB ELISA, IRF3, AP1, and GFAP western blotting and cytokines/chemokines gene expression real time qRT-PCR (4–6/group). A second group of pups were killed at 24 h (P9) or 7 days (P15) after poly I:C to assess astrocytic (GFAP) and microglia (Iba1) activation in the hippocampus, thalamus and cortex using immunohistochemistry, and gene and protein expression of cytokines/chemokines using real time RT-PCR and MSD, respectively (4–6/group). Non-parametric analysis was applied. Six hours after poly I:C, caspase-3 and -8 activities in cytosolic fractions were 1.6 and 2.8-fold higher in poly I:C-treated than in NS-treated female mice, respectively, while gene expressions of pro-inflammatory cytokines were upregulated in both sexes. After poly I:C, IRF3 nuclear translocation occurred earlier (6 h) in female mice and later (14 h) in male mice. At 14 h after poly I:C, only male mice also had increased nuclear NFκB levels (88%, p < 0.001) and GFAP expression coinciding with persistent IL-6 and FAS gene upregulation (110 and 77%, respectively; p < 0.001) and IL-10 gene downregulation (-42%, p < 0.05). At 24 h after poly I:C, IL-1β, CXCL-10, TNF-α, and MCP-1 were similarly increased in both sexes but at 7 days after exposure, CXCL-10 and INFγ were increased and IL-10 was decreased only in female mice. Accordingly, microglial activation persisted at 7 days after poly I:C in the hippocampus, thalamus and cortex of female mice. This preliminary study suggests that TLR3 activation may produce in the developing neonatal mouse brain a sexually dimorphic response with early activation of caspase-dependent pathways in female mice, activation of inflammatory cascades in both sexes, which then persists in female mice. Further well-powered studies are essential to confirm these sex-specific findings

Inflammation in the immature brain: The role of Toll like receptors

Infection/inflammation and/or hypoxia-ischemia (HI) are major causes of perinatal brain injury. Toll-like receptors (TLRs), important components of innate immunity, have been shown to be involved in brain injury, both after infectious and endogenous, non-infectious, stimuli. The overall aim of this thesis was to study the expression of TLRs in the immature brain, choroid plexus and endothelial cells after inflammatory stimuli and/or HI, and to investigate the role of TLRs, their adaptor proteins MyD88 and TRIF in brain damaging processes after HI. TLR stimuli, HI or a combination of them both was performed on mice at postnatal day 9. Brain injury and inflammatory responses were evaluated with immunohistochemistry, RT-qPCR and cytokine analyses. All investigated TLRs were expressed under basal conditions in the neonatal brain and several of the receptors were regulated in the brain, choroid plexus and blood brain barrier after inflammatory stimuli and/or HI. Additionally, systemic stimulation of TLR 1/2 and TLR 4 decreased the expression of occludin, a tight junction protein, in the choroid plexus. TLR 2 was constitutively expressed in astrocytes in white matter and in neurons in the paraventricular nucleus and contributed to brain damage following HI. In contrast, MyD88 and TRIF did not appear to play a role in the injury process after HI alone. Both lipopolysaccharide (LPS), a TLR 4 ligand, and Poly I:C, a TLR 3 ligand, sensitized the brain to HI in wild type mice. This effect was blocked in MyD88 and TRIF deficient mice. Both Poly I:C and LPS increased the pro-inflammatory cytokine levels in the brain and this increase was blocked/reduced in the TRIF and MyD88 deficient animals. To conclude, TLRs are expressed under basal conditions and regulated during inflammation in the brain as well as in choroid plexus and blood brain barrier. In particular, we found that TLR 2 contributes to injury following HI, indicating that it has a function in sterile inflammation in the neonatal brain. Further, both MyD88 and TRIF play essential roles in LPS/Poly I:C-sensitized HI neonatal brain injury. These findings suggest that TLRs are important in both physiological and pathological processes in the immature brain and may provide novel targets for neuroprotective therapies in the future

Modeling and quality assessment of nystagmus eye movements recorded using an eye-tracker

Mathematical modeling of nystagmus oscillations is a technique with applications in diagnostics, treatment evaluation, and acuity testing. Modeling is a powerful tool for the analysis of nystagmus oscillations but quality assessment of the input data is needed in order to avoid misinterpretation of the modeling results. In this work, we propose a signal quality metric for nystagmus waveforms, the normalized segment error (NSE). The NSE is based on the energy in the error signal between the observed oscillations and a reconstruction from a harmonic sinusoidal model called the normalized waveform model (NWM). A threshold for discrimination between nystagmus oscillations and disturbances is estimated using simulated signals and receiver operator characteristics (ROC). The ROC is optimized to find noisy segments and abrupt waveform and frequency changes in the simulated data that disturb the modeling. The discrimination threshold, 휖, obtained from the ROC analysis, is applied to real recordings of nystagmus data in order to determine whether a segment is of high quality or not. The NWM parameters from both the simulated dataset and the nystagmus recordings are analyzed for the two classes suggested by the threshold. The optimized 휖 yielded a true-positive rate and a false-positive rate of 0.97 and 0.07, respectively, for the simulated data. The results from the NWM parameter analysis show that they are consistent with the known values of the simulated signals, and that the method estimates similar model parameters when performing analysis of repeated recordings from one subject